Conventionally, there have been various applications available for an electric stage which is capable of moving in the X-axis, Y-axis, and Z-axis directions as well as rotating about each of the axis, the X axis, the Y axis, the Z axis being defined as three axes perpendicular to one another in a rectangular coordinate system.
One of the specific examples of an image pickup device having a camera shake correction function may include a camera. As the shake correction function for cameras, there is known a camera shake correction function for detecting, using a shake detector such as an angular velocity sensor, a shake in a camera pitch direction and a shake in a camera yaw direction, and shifting, in a horizontal direction and in a vertical direction, part of an image pickup optical system or the imaging element independently of each other in a direction of canceling the shake, in a plane perpendicular to a photographing optical axis based on a signal indicative of the detected shake, to thereby correct blurring of an image on an image pickup plane of an imaging element.
A camera shake correction mechanism for realizing the camera shake function described above employs a driving unit for moving some photographing lenses or the image sensor itself in the horizontal direction and the vertical direction in a plane perpendicular to the photographing optical axis. The driving unit needs to be precisely driven (micro driven) as being operated following a camera shake, and also required to perform accurate positioning of the movable body (positioning on the image pickup plane) relative to the photographing lens, when driven. Further, the driving unit is required to have a large drive force in order to obtain an acceleration necessary for control against the gravitational force of the mobile body, and also to have a self-retainability capable of retaining a position of the movable body even after power-off. The driving unit is, naturally, required have a mechanism which is compact and inexpensive, rather than having a complicated mechanism. On the other hand, there is a demand for a driving mechanism capable of driving the movable body in a direction perpendicular to an image pickup plane in order to perform camera shake correction in further advanced macro photographing and focal point detection in the contrast system.
Other specific examples thereof include a stage in a microscope for placing an object to be observed. Such a stage is required to move freely in the XY plane so as to move a desired position of the object to be observed into the observation field of the microscope. Further, the stage is provided with a mechanism capable of precisely moving the stage in the Z-axis direction perpendicular to the XY plane so as to make adjustments in focal positioning.
For example, Japanese Patent Document Laid-Open No. 2008-129326 discloses a driving mechanism which includes: a plurality of substrate supporting projections each having a smooth surface at the distal end thereof, the substrate supporting projections being formed on a base yoke plate; a pressing pin having a smooth surface at the distal end thereof, the pressing pin being pressed by a coil spring, the substrate supporting projections and the pressing pin clamp-holding a movable portion therebetween; a coil provided on the movable portion side; and a magnet provided on the base yoke plate side, the coil and the magnet forming a voice coil motor (hereinafter, referred to as VCM), to thereby allow movements in the X-axis direction (horizontal direction) and in the Y-axis direction (vertical direction) within a plane defined by the end surfaces of the base supporting projections and also allow rotation about an axis perpendicular to the XY plane.
However, in this mechanism, the movable frame is constantly under a frictional force of pressure-support, which leads to a problem that the VCM for moving the movable frame is reduced in power due to the frictional force. Further, the movable frame is held by a fixed frame via the frictional force of pressure-support when the operation of the VCM is stopped. However, if the holding power is increased so as to increase the holding performance, the frictional force also increases, which may further reduce the power of the VCM. In addition, although this driving mechanism allows, with a simple configuration, movements in the X-axis direction (horizontal direction) and in the Y-axis direction (vertical direction) and also allows rotation about an axis perpendicular to the XY plane, driving in a direction perpendicular to the XY plane (optical axis direction of the camera, i.e., Z-axis direction) remains unrealized. If the drive control in the Z-axis direction can be realized, it can be applied to a vibrating operation (hereinafter, referred to as wobbling) in the Z-axis direction for focus detection of the camera, a focusing operation, or a camera shake correction operation in the optical axis direction which is effective in macro photography.
Japanese Patent Application Laid-Open No. 2010-282028 discloses a lens unit which includes an actuator (in the form of VCM) for linearly moving a transducer with respect to a stator, in which the transducer and the stator are pressed against each other when the actuator for moving does not generate a drive force, while the pressing force between the transducer and the stator is cancelled by an actuator for the breaking part (specifically, a piezoelectric body) when the actuator for moving generates a drive force.
However, this driving mechanism is a single-axis driving mechanism for driving a transducer in the Z-axis direction (optical axis direction) relative to the stator, without implementing movements in multi-degree of freedom. In particular, the movement in the direction of the pressing force is completely out of control. When the movable frame is driven relative to the fixed frame by the actuator for moving, the pressing force is released, with the result the play in the mechanism randomly varies in position.
Japanese Patent Document Laid-Open No. 2010-191298 discloses a microscope including: a stage for placing thereon an object having a plurality of observation points; an automatic focusing device; an objective lens driving portion for drive-controlling the observation positions; and an offset lens driving portion. According to this microscope, when the automatic focusing device detects a focus error at a certain observation position, the relative position of the observation position in the optical axis direction is calculated based on the focus signals obtained at the plurality of observation positions that have been already observed, so as to control the lens driving portion and the offset lens driving portions, to thereby perform focusing operation.
However, in this microscope, a sample stage driving mechanism for position adjustment in the sample plane and a lens driving mechanism for focus position adjustment in the optical axis direction need to be provided separately from each other. As a result, the microscope is increased in size and becomes more complicated in configuration.